Steam generator with spherical steam generating chamber



April 9, 1968 N. D. ROMANOS 3,376,858

STEAM GENERATOR WITH SPHERICAL STEAM GENERATING CHAMBER Filed Dec. 2", 1965 2 $heet 1 INVENTOR.

NICHOLAS a POMANOS ATTORNEY FiledDec. 27, 1965 April 9, 1968 N. D. ROMANOS 3,376,858

STEAM GENERATOR WITH'SPHERICAL STEAM GENERATING CHAMBER I 2 Sheets-Sheet 2 5 INVENTOR.

NICHOLAS Q ROMA/V05 United States Patent 3,376,858 STEAM GENERATOR WITH SPHERICAL STEAM GENERATING CHAMBER Nicholas D. Romanos, Chattanooga, Tenn., assignor to Combustion Engineering, Inc., Windsor, Conn., a corporation of Delaware Filed Dec. 27, 1965, Ser. No. 516,595 7 Claims. (Cl. 122-62) The present invention relates to shell and tube type heat exchangers. More particularly, the invention relates to a shell and tube type heat exchanger wherein liquid is vaporized by indirect heat exchange with a fluid heating medium.

Heat exchangers are commonly employed in vapor generating systems when it is desired to transfer heat from a primary fluid to a secondary fluid without the two fluids coming in contact. This is accomplished by passing the fluids along opposite sides of a heating surface which provides an effective heat flow path from one fluid to the other. In normal practice, the heating surface usually comprises a tube bundle consisting of banks of tubes that conduct the primary fluid and are submerged in the secondary fluid.

At the present time high temperature fluids are made available for vapor generating purposes in such industries as petroleum refining, chemical manufacturing, among others. Such fluids are also available in nuclear installations wherein the primary fluid which has been used for cooling the reactor is cused to give up heat to the secondary fluid in heat exchangers of this type. With the present tendency being to develop vapor generators of greater capacity operable .to generate vapor at higher pressures it has been necessary to increase the size of the heat exchangers employed and also to employ materials of greater strength in order to withstand the pressures to which these units are subjected. The result of such atendency is to markedly increase the manufacturing costs of vapor generators of known design in order to satisfy the size and strength demands made upon these units.

Accordingly it is an object of the present invention to provide a shell and tube type heat exchanger adapted for use as a high capacity vapor generator for producing vapor at high pressure which avoids the deficiencies of vapor generators heretofore known to the art.

Another objection of the invention is to provide a heat exchanger of unique design permitting the use of lighter gauge materials in the production of high pressure vapor.

Still another object of the invention is to provide a heat exchanger of unique design that is characterized by compactness of form and efiiciency of operation.

Still another object of the invention is to provide a compact heat exchanger that is characterized by enlarged, unrestricted flow areas whereby the flow of secondary fluid therethrough is unimpeded.

Yet another object of the invention is to provide a compact heat exchanger that is capable of delivering dry vapor without the need for complex, expensive vapor separating equipment.

Other objects and advantages will appear from the following description of one embodiment of the invention, and the novel features will be particularly pointed out hereinafter in connection with the appended claims.

The invention is described with reference to the accompanying drawings wherein:

FIGURE 1 is a vertical section of a heat exchanger constructed in accordance with the invention;

FIGURE 2 is a plan section taken along line 22 of FIGURE 1; and

FIGURE 3 illustrates a typical tube support element.

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3,376,858 Patented Apr. 9,. 1968 As shown in the drawings the heat exchanger 10 includes a containment shell 12 that is spherical in configuration and forms an interior chamber within which the generation of vapor occurs. The shell 12 is preferably positioned with its axis extending generally vertically and is adapted to contain -a body of vaporizable liquid, the level 14 of which divides the chamber into a liquid space 16 and a vapor space 18. A vapor nozzle 20 penetrates the shell 12 at its top to communicate with the vapor space 18 in order to conduct vapor to its intended point of use. A manway 22 having a threadedly connected cover 24 may also be provided in the upper portion of the shell 12 to permit access to the chamber.

A generally annular tube bundle 26 is positioned in the lower portion of the shell chamber such that it will be substantially completely submerged in the liquid space 16 during operation of the heat exchanger. The tube bundle 26 comprises a plurality of vertical rows of horizontally extending U-shaped tubes 28 that are adapted to conduct heating fluid and which are connected for parallel fluid flow by means of a fluid manifold 30. The tube bundle 26 is surrounded by plate means forming an annular bafile 32 that is concentrically spaced from the wall of the shell 12 thereby providing an annular downcomer passage 34. As shown, the baflle 32 is spaced from the bottom of the shell 12 in order to establish fluid communication with the interior section 36 of the chamber that contains the tube bundle 26 such that recirculation of liquid can occur in an unimpeded manner.

At the bottom of the interior,'or vapor generation, section 36 of the liquid space 16 is located an annular feedwater inlet tube 38 having its surface provided with spaced openings 40 that effect the discharge of liquid into the shell chamber. As shown, one end of the tube 38 is attached to a feedwater nozzle 42 that penetrates the shell and connects the tube to a source of vaporizable liquid (not shown).

The fluid manifold 30 that connects the tubes 28 comprises a generally hollow cylinder that penetrates the bottom of the shell 12 and is disposed in coaxial relation thereto. The upper and lower ends of the manifold are closed by hemi-elipsoidal closure heads, 44 and 46 respectively, the former being provided with a manway 48 and threadedly connected cover 50 for permitting access to the interior of the manifold. The lower end of the manifold 30, externally of the shell 12, is provided with radially extending heating fluid inlet and outlet nozzles, 52 and 54 respectively, that direct heating fluid to and from the heat exchanger. The manifold 30 is further provided with a partition plate 56 that divides its interior into fluidly distinct heating fluid inlet and outlet compartments 58 and 60. An enlarged central opening 62 is provided in the plate 56 which, together with a concentrically disposed fluid duct 64 and sleeve 66 connect the heating fluid inlet compartment 58 with the inlet nozzle 52. The flow circuit for the heating fluid comprises the annular tube bundle 26 that includes the U-shaped tubes 28 that are connected to the manifold 30. Allof the tubes 28 have U-bends located in vertical planes, as illustrated in FIGURE 1, and have both ends connected to the manifold 38 on opposite sides of the partition plate 56 such that there will be a continuous flow of heating fluid through the tubes from the inlet compartment 58 to the outlet compartment 60. As best shown in FIGURE 2, the tubes 28 are formed so as to provide the maximum amount of heating surface that can be accommodated within the shell 12. This is accomplished by'providing the opposed legs of each tube 28 with a first, straight portion 68 that includes the ends of the tubes and that radially communicates with the wall of the manifold 30. The remainderof the opposedlegs and U-bend, indicated as the portion 70, are laterally offset from their vertical plane along a circular arc outwardly toward the wall of the shell 12 with a smooth transition section 72 being provided between the portions 68 and 70. By extending the length of the tube circuits in this manner, more efficient use of the volume of the containment chamber can be obtained.

Support for the tube bundle is provided by concentric rows of circumferentially spaced, vertically elongated tube supports 74 that, as shown in FIGURE 3, are provided with apertures 76 that receive the tubes 28. The tube supports 74 are formed of 'a width capable of being received between adjacent rows of tubes 28 and, as shown in FIGURE 2, can be conveniently positioned between the tubes by locating them along circular arcs. The supports are connected at their upper and lower ends by annular structural members 78 and =80, respectively, the latter of which are vertically supported on support ribs 82 that extend radially from the wall of the manifold 30.

In order to install the tubes 28 of tube bundle 26, a plurality of tubes indicated in FIGURE 2 by the space 84 must be omitted. This space represents only a small fraction of manifold wall space which is left devoid of tube seat apertures for connecting the tubes 28 and, therefore, a commensurate amount of heating surface. Since the amount of heating surface omitted from the tube bundle in this area is so slight it does not materially affect the over-all efficiency of the unit.

Means are provided in the instant arrangement to permit easy access to the tube ends within the manifold 30, especially those ends located in the heating fluid outlet compartment 60 where work space is at a minimum due to the presence of the fluid duct 64. As shown in FIGURE 1, the fluid duct 64 is connected at its lower end to the heating fluid inlet nozzle 52 by means of a right angle section and extends to a level spaced below that portion of the manifold 30 that attaches the lower ends of the tubes 28. The upper end of the duct 64 is open and is caused to communicate with the heating fluid inlet compartment 58 by means of the sleeve 66 which is telescopically received by, and vertically slideable along, the duct. The sleeve is provided at its upper end with an annular flange 86 having circumferentially spaced apertures that, together with similar apertures in the plate 56, accommodate threaded connectors indicated by the center lines 88, so as to detachably connect the sleeve to the plate. The lower end of the sleeve 66 is provided with an annular flanged section 90 having an inner surface that slideably engages a mating surface 92 on the exterior of the upper end of the duct 64. It is contemplated to form the sleeve 66 or at least its lower flanged section 90 of 'a material having a different coefficient of thermal expansion than that which forms the duct 64 whereby, when the heat exchanger is in operation and the duct and sleeve subjected to elevated temperatures, an expansion seal will be created between the surfaces 90 and 92. Conversely, when the unit is removed from service and in a cooled state, the seal will be automatically broken by the relative thermal contraction between the materials forming the surfaces 90 and 92 whereupon the sleeve 66 can be removed from position merely by disconnecting the threaded connectors 88 that connect the sleeve flange 86 to the plate 56 and lowering the sleeve along the duct to the bottom of the manifold interior. In this manner easy access can be had by a workman for inspecting or repairing the ends of all the tubes that connect to the manifold 30.

In the upper portion of the vapor space 18 adjacent the vapor discharge nozzle 20 may be disposed a substantially continuous annular ring of plate or screen drier elements 94 through which vapor must pass in flowing to the nozzle 20. It is the purpose of these driers to remove any fine liquid particles retained in the vapor that emerges from the vapor space 18. As shown in FIGURE 2, each drier element 94 has a trapezoidal configuration and is re movably attached at its inner end to a horizontally disposed, substantially circular baftle plate 96 with the outer ends thereof attached to the inner surface of the shell 12 by means of brackets 98. The completed assembly is frusto-conical in shape and is vertically supported by a plurality of spaced support rods 100 that are connected between the baffle plate 96 and the upper manifold closure head 44. In operation, the relatively hot heating fluid enters the inlet nozzle 52 and is conducted to the inlet compartment 58 by the duct 64 and sleeve 66. The heating fluid then enters the upper ends of the tubes 28 in the tube bundle 26, flows through the tubes, out their lower ends into the outlet compartment 60 from whence it is conducted through the outlet nozzle 54. At the same time vaporizable liquid is discharged into the shell chamber through openings 40 in the feedw'ater tube where it establishes a body of liquid having its level 14 closely adjacent the equator of the spherical chamber such that all, or substantially all, of the tubes 28 are immersed in the liquid. Due to the enlarged surface area of boiling liquid the vapor is released therefrom in large amounts but at relatively low velocity. The vapor rises in the vapor space 16 where any liquid particles retained therein are removed by gravity. If found to be desirable, screen driers 94 may be employed to mechanically remove any fine liquid particles contained in the vapor before it exits the unit through the vapor nozzle 20. The amount of space available in the spherical chamber, however, will be suflicient to deliver vapor having acceptable dryness for most purposes.

Consequently, due to the unique structural arrangement of the present invention wherein the containment shell in which vapor generation occurs is formed as a a sphere several important advantages are realized over vapor generators of the prior art. Firstly, the amount of floor space necessary for mounting a unit of the instant type is reduced by approximately 50% over that required for mounting conventional cylindrical units of similar capacity. Secondly, the wall thickness of the containment shell need be only a fraction of that of a cylindrical shell to withstand equivalent pressures thereby materially reducing the fabrication costs of the unit. Moreover, by employing a spherical containment shell in which a large vapor release surface is provided the need for complex,'expensive vapor separation equipment is avoided since adequate gravity separation is attainable.

It will be understood that various changes in the details, materials, and arrangements of parts which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

What is claimed is:

1. A heat exchanger wherein liquid is vaporized by indirect heat transfer from a fluid heating medium comprising: a spherically formed shell defining a substantially closed containment chamber; means for introducing liquid to said chamber to provide a liquid body therein defining 'a liquid space and a vapor space, each of said spaces occupying substantially the entire transverse area of said chamber and said vapor space having suflicient height to effect gravity separation of a major portion of the liquid contained in the vapor-liquid mixture produced therein; a vapor outlet from said vapor space; an axially disposed, generally cylindrical manifold penetrating said shell and including means dividing the interior of said manifold into separate fluid inlet and outlet compartments; a substantially annular tube bundle disposed in said liquid space including a plurality of circumferentially spaced rows of U-tubes having their respective ends disposed in vertical planes and radially attached to said manifolds; means connecting one end of each of said U-tubes in communication with one of said compartments and the other end thereof in communication with the other of said compartments and the legs of said U-tubes being curvilinearly offset from the planes of said ends in mutually spaced relation.

2. A heat exchanger as recited in claim 1 wherein said liquid level is disposed in proximity to the equator of said shell.

3. A heat exchanger as recited in claim 2 including an annular baffle and disposed in said liquid space about the periphery of said tube bundle, said baffle being open at both ends and having its wall closely spaced from the wall of said shell to form an interior vapor generation section and an exterior downcomcr passage.

4. A heat exchanger as recited in claim 1 wherein said U-tubes each comprise a straight portion including the ends thereof that are disposed in radially extending relation from the wall of said manifold and a remaining portion that is offset from the plane of said ends along the are of a circle.

5. A heat exchanger as recited in claim 1 including a generally cylindrical manifold penetrating said shell along the axis thereof; means closing the ends of said manifold; heating fluid inlet and outlet nozzles attached to the wall of said manifold and disposed exteriorly of said chamber; laterally extending plate means dividing the interior of said manifold into axially spaced heating fluid inlet and outlet compartments; a central opening in said plate means; and coaxially elongated conduit means concentrically spaced from the wall of said manifold and extending through one of said compartments with its opposite ends connecting between one of said nozzles and said central opening.

6. A heat exchanger for the indirect transfer of heat betwen two fluid mediums including a shell adapted to contain one of said mediums; a plurality of U-shaped tubes mounted in said shell for conducting the other of said mediums; a manifold connecting said tubes for parallel fluid flow comprising an axially elongated, generally and outlet nozzles attached to said Wall adjacent one and outlet nozzles attached to said wall adjacent one end end thereof, laterally extending plate means intermediate the ends of said wall dividing the interior of said manifold into axially spaced inlet and outlet compartments,

means forming circumferentially spaced openings about said wall for connecting the ends of said U-shaped tubes in fluid communication between said compartments, a central opening in said plate means, elongated conduit means concentrically spaced from said Wall and extending through one of said compartments with its opposite ends connecting between one of said nozzles and said central opening, said conduit means including a duct rigidly secured with respect to said manifold wall, an axially movable sleeve having one end adapted for telescopic reception over one end of said duct, and the other end arranged for detachable connection to said manifold Wall, mating surfaces on said one ends of said duct and sleeve arranged for sealing engagement during operation of said heat exchanger, said mating surfaces being formed of materials having different coeflicients of thermal expansion such that one is expanded into sealing engagement with the other when said heat exchanger is operating.

7. A heat exchanger as recited in claim 6 wherein said conduit means includes a rigid duct having one end connecting to one of said nozzles and its other end axially spaced from said plate means, an axially movable sleeve telescopically received on said duct and extending from the top of said duct to said plate means, detachable means connecting the upper end of said sleeve to said plate means, concentrically engageable surface means on said duct and said sleeve each being formed of materials having different coeificients of thermal expansion whereby said surfaces engage in sealed relation when exposed to an increase in temperature.

References Cited UNITED STATES PATENTS 2,494,767 1/ 1950 Lindsay 12234 X 2,508,729 5/1950 Stein -163 3,012,547 12/1961 Ostergaard et al 122-32 3,130,713 4/1964 Sprague 122--32 3,213,833 10/1965 Cunningham et al. 122-34 KENNETH W. SPRAGUE, Primary Examiner. 

1. A HEAT EXCHANGER WHEREIN LIQUID IS VAPORIZED BY INDIRECT HEAT TRANSFER FROM A FLUID HEATING MEDIUM COMPRISING: A SPHERICALLY FORMED SHELL DEFINING A SUBSTANTIALLY CLOSED CONTAINMENT CHAMBER; MEANS FOR INTRODUCING LIQUID TO SAID CHAMBER TO PROVIDE A LIQUID BODY THEREIN DEFINING A LIQUID SPACE AND A VAPOR SPACE, EACH OF SAID SPACES OCCUPYING SUBSTANTIALLY THE ENTIRE TRANSVERSE AREA OF SAID CHAMBER AND SAID VAPOR SPACE HAVING SUFFICIENT HEIGHT TO EFFECT GRAVITY SEPARATION OF A MAJOR PORTION OF THE LIQUID CONTAINED IN THE VAPOR-LIQUID MIXTURE PRODUCED THEREIN; A VAPOR OUTLET FROM SAID VAPOR SPACE; AN AXIALLY DISPOSED, GENERALLY CYLINDRICAL MANIFOLD PENETRATING SAID SHELL AND INCLUDING MEANS DIVIDING THE INTERIOR OF SAID MANIFOLD INTO SEPARATE FLUID INLET AND OUTLET COMPARTMENTS; A SUBSTANTIALLY ANNULAR TUBE BUNDLE DISPOSED IN SAID LIQUID SPACE INCLUDING A PLURALITY OF CIRCUMFERENTIALLY SPACED ROWS OF U-TUBES HAVING THEIR RESPECTIVE ENDS DISPOSED IN VERTICAL PLANES AND RADIALLY ATTACHED TO SAID MANIFOLDS; MEANS CONNECTING ONE END OF EACH OF SAID U-TUBES IN COMMUNICATION WITH ONE OF SAID COMPARTMENTS AND THE OTHER END THEREOF IN COMMUNICATION WITH THE OTHER OF SAID COMPARTMENTS AND THE LEGS OF SAID U-TUBES BEING CURVILINEARLY OFFSET FROM THE PLANES OF SAID ENDS IN MUTUALLY SPACED RELATION. 